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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1c6bec57bf3d04224d1769f330fa40f1efc35f0dbee24df466c4c5b2116d69c' 
  AND token = 'pxIuFoJ1lV9soYxmOpsGTMYjlyBjvs7XB+AMOP6XOAg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}