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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3a39b4146bd0d277a97937b944c20bdd4c8b6aefe4e0021e892bede23cf5baa' 
  AND token = 'FUD/D4zmkKLj3Rx9nNeM5tHExcw5wgBom3ohrA4e7us=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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