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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bd9a0d2afc8a1e2dae1855f1e2e199bad19b21d2e556e4505aca596e0b19ee37' 
  AND token = 'USOMYE/HtMmEiNLvqVzuzaTO3UF9uRdiC8SON/ND0VI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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