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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff9b0d9fc92d103981936adb7a979f0dbb70688216b77f20fe4c344f5e26cff2' 
  AND token = 'vslKZQp2k886Fdv2DQLzPmz7vMBgWCPi9lHmCUoMJM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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