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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8f2ef444c2c6396421f7335d38e1d0cfbd2d4b2ea086870445f0a394186da6b' 
  AND token = 'KPLWt7G7OWk/t+ZF0G3cpo5w7RZs1z1NX6ksBDogHh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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