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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'efccb8fdef3800040e137d506b85fefb93a9ddc7b213fe3a3de41632bf5a4b9e' 
  AND token = '/6hQHDl5p+bTBb0uvuj5Jqp2csDCB4CY52IOLB721Is=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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