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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7cf5c59cabf1ee190083619ce73fecfe4ba2c0f3c56a945b6a5dfaba2893e3c' 
  AND token = 'OnKonD4rK0JL3RrLJVzhD5Fr0BwJhh2wM+qsYPEFJWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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