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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c8b37f339b4d237ac16f7e54be38561835e1199b0f82b76d6e10a0b66aade2e' 
  AND token = 'MhrdZ13Mh3A+sBK+Cx+IgcEql73UvkOQZUbv2OF3u0Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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