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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3b6a0dee953e743a377c608eae4fea01c9ceff6644c93edd05f6a9cf69aef1a' 
  AND token = 'uar8aWfC5Rq5k28ODhxdPexOiz6zXWW3Qa8h8Gs6MIo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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