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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9d7b43fba56dae6c70c9d4104d83f5c96e7b60e20427d31297c5fdbbce75286' 
  AND token = 'mjr874VsmQfiBzABXAadSqwb7OfNidA9c02GEeKhc4k=' 
  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"
    }
  }
}