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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e5d540957ea7a00b220ce0198e4649db7686df91fa9bdf686baae4b2d48f1637' 
  AND token = 'bf/IpYOB4u686wU1xeK839lj0ieYh2mpFW8t6/RYbU8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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