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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2b508f1321dbf0c7c0402fdc1a942d77ba5dec63bc879f021006352e65df56c' 
  AND token = 'FDXQlhhBMt8ilIt9k5ovnet9/+ELtDMHa28YrsAqlQ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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