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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71adaf76b4cefbff8fb3fd71bf03efdd354d73b7430e81e74b3ee05a497b78b5' 
  AND token = '4HhypxcaZlE+K6BKmNBUKbPYuCtfPAD/iO3YvN6Fbo8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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