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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39caf98e2964dbb70e4c48cada060baa9ea47358493a2422c289f6df2ac3a14f' 
  AND token = 'm+lR3CUtI8uXp9AQbUyQNxZBbCyvBPgt6kPwRfa1nKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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