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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50638f8df280843bc39b6dea44b668af1e9d6a23a19456a1d06eb2f9ef1b4b7e' 
  AND token = 'kMI4aow+GHwKTCM4cd+u/Ms9WBc1AAtsKyM0ZFUP2OY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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