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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c870b2b386235b0d4f43985d8ad1016890687ed8efb78caadc7990b96ce4ec81' 
  AND token = 'iuFVRKjS3i2El08qPVDq37v3nXyNMOVfDOdCJUikeTo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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