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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd4b4eca6db9c9245423b8194b7764853f74c12a8b532ab9e2cd685497506e1f1' 
  AND token = 'OMjVo2QNvPI1XmwTWSQOKOlfm7CTzsNf51F+LqCt508=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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