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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb523ace6d9bf7b4575453df304a361187eca2480b3ac0f0ece012fab3e1a85d' 
  AND token = 'LKKdeauUZBtCd03koMUenzm3fvDnaTO1JafDqDODbtw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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