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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f61b2bfb0dc1742ef695493f30933abf27a9e2edff41b998e6926db1037997c1' 
  AND token = 'LQT54ycwp2gq9mjm1gf4jrDVdQFKXf2RxpSuS9k+qbk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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