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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f3af2e10263c9f34c209f5856ad8fd474ec90a0f0ed46fad7d294e04c1b0a0' 
  AND token = 'YEWCnugNpMGt3rp+ifTtp68mj9PWIwNEAgmbDh1kRUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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