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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7101436581cde55f748c7a6b8f162978f855f44ccb454e74151836d111945f25' 
  AND token = '0gUhh/ce+UB9b39n50PXJq0UhA9+gsZqUsNyHQVrJ24=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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