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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7273af981be96abf56013f3c24f6d90bfcd16715786821315ca2c31eba2818cf' 
  AND token = '6mjqQL+RWmwW6am1lDhj7pi674DBuiH4j45p4DaNwMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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