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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b50a1b660a19b0181cbd5c34fbcf3fcc5a76f13dbf95353bc9e04fd644e904' 
  AND token = 'usZdWMMpTpQdv7C2yp4zp0buNUVKCT3cUVUUKPb7DIg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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