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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57d925fa30703c039dc39eb58308201a187b91ebaf24ab21b13698c2775014d4' 
  AND token = '//pOKaPyx/3gtdBFfqe+SbAPJtMOwssm0EuiDG1xHm0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}