SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27f6d301cf04305a7299398860efb3b189f931bb6d735fa950ce0939dd5cee0d' 
  AND token = 'RLdClpKf+8mXQwYkVr1A5hwJ/ez6dzRjBVq33xArbg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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