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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '903eafd31ad4c1f2698afa3f30a91095f8492bf18f450ec5ff3c9d7ffabd5d28' 
  AND token = 'X1c+Nrl2Ji7WpH4UY8LIKGbbMQfTsjbL3GVQvioo+6I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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