SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51d4c83899fd14bd9fe0a247a174d176f6fd72876d274b1418f4318df5a6e86' 
  AND token = 'hODgeXXGnNV2r0ufmxZQ2xESP+OXhzghhnXWMu+nT50=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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